The present invention relates to a control valve for use in a brake booster.
In such brake boosters, the control valve in a first mode of operation responds to control the communication of fluid through a hub from a first source of fluid to both sides of a movable wall that separates a cavity in a housing into first and second chambers and in a second mode of operation responds to control fluid from a second source to the second chamber to create a pressure differential across the movable wall. The pressure differential acts on the movable wall to produce an output force corresponding to an input force applied to operate the control valve in the second mode.
In an effort to reduce the overall dimension of the control valve it has been disclosed in U.S. Pat. No. 4,237,770 issued Dec. 9, 1980 that a resilient disc would respond to control the communication of fluid between first and second chambers to develop an operational pressure differential in response to an operator input. It was evident that the size of the control valve could be further reduced if the slot in the hub for the retention key for the plunger were eliminated.